Estimating the Probability of Compound Discharge/surge Events in a Complex Estuarine System Under Data Constraints

<p>Compound flooding may result from the interaction of two or more contributing processes, which may not be extreme themselves, but in combination lead to extreme impacts. Estuarine environments are particularly prone to compound flooding due to the interplay between coastal storm surge and river discharge processes, both often being driven by the same storm event. A detailed understanding of compounding mechanisms, including the dependence between flooding drivers, is necessary to avoid flood risk miscalculations when building/upgrading flood defences to mitigate risks associated with high impact events. Here, we use statistical methods to assess compound flooding potential in Sabine Lake, TX. Sabine Lake receives discharge from two rivers and is connected to the Gulf of Mexico coast through Sabine Pass. These geographic characteristics make it susceptible to compound flooding. We employ several trivariate statistical models (and simplified bivariate models for comparison) to examine the sensitivity of results to the choice of data pre-processing steps, statistical model setup, and outlier removal. We define a response function that represents water levels resulting from the interaction between discharge and storm surge inside Sabine Lake, and explore how the water level response is affected by including or ignoring dependencies between the contributing flooding drivers. Our results show that accounting for dependencies leads to water levels that are up to 30 cm higher for a 2% annual exceedance probability (AEP) event and up to 35 cm higher for a 1% AEP event, compared to assuming independence. We also find notable variations in the results across different sampling schemes, multivariate model configurations, and sensitivity to outlier removal. This highlights the need for testing various statistical modelling approaches in order to reliably capture potential compounding effects, especially under data constraints.</p><p> </p>

Impacts of Storm Surges on Hydrodynamics and Salinity of Sabine Lake and Sabine River Diversion Canal

In this study, a hydrodynamic and salinity transport model was developed for simulations of Sabine Lake water system located on the Texas-Louisiana border. The target simulation area ranges from Sabine River near Deweyville, TX as the north boundary to the Gulf of Mexico as the south boundary, and from Neches River near Beaumont, TX as the west boundary to part of Gulf Intracoastal Waterway (GIWW) and Sabine River Diversion Canal (SRDC) as the east boundary. The entire area includes several major water bodies, such as Sabine Lake, Sabine River, Sabine Pass, Sabine Neches Canal (Ship Channel), and part of GIWW and SRDC. The SRDC supplies fresh water to the area industry, mainly petrochemical. High salinity in SRDC could significantly affect the daily production of the industry. The major purposes of this study is to use the validated hydrodynamic and salinity transport model to assess and predict the salinity in SRDC under severe weather conditions such as hurricane storm surges. Measurement data from NOAA and USGS were used to calibrate the boundary conditions as well as to validate the model. Two different levels of storm surges each lasting for 24 hours were simulated, 0.5 and 1 meter, respectively, and the salinity in SRDC was monitored and compared to analyze the storm surge threats on SDRC water quality. The result shows that it took about 2 days for the salinity reaching SRDC under the 1m storm surge condition and about 3 days under 0.5m surge condition and the salinity value could reach as high as 5 to 10 ppt.

Calibration and Validation of Hydrodynamics and Salinity Transport Model for Sabine Lake Water System

In this study, a hydrodynamic and a salinity transport models were developed for simulations of Sabine Lake water system located on the Texas-Louisiana border. The target simulation area includes several major water bodies, such as Sabine Lake, Sabine River, Sabine Pass, Sabine Neches Canal (Ship Channel), and part of Gulf Intracoastal Waterway (GIWW) and Sabine River Diversion Canal (SRDC). The SRDC supplies fresh water to the area industry, mainly petrochemical. High salinity in SRDC could significantly affect the daily production of the industry. Two-dimensional (2D) depth-averaged shallow water equation set and 2D depth-averaged salinity transport equation were used for developing the hydrodynamic and salinity transport numerical models in order to carry out the simulation. The major purposes of this study are to calibrate and validate hydrodynamic and salinity transport models in order to assess and predict the salinity in SRDC under severe weather conditions such as hurricane storm surges in future study. Measurement data from National Oceanic and Atmospheric Administration (NOAA) and United States Geological Survey (USGS) were used to calibrate the boundary conditions as well as to validate the model. Boundary conditions were calibrated at locations in Sabine Pass and in the north edge of the lake by using water–surface elevation data. Hydrodynamic model was validated at the USGS location using water–surface elevation data. Then, the simulation estimations of water surface level and salinity were compared at three locations, and the results show the accuracy of the validated model. Parallel computing was conducted in this study as well, and computational efficiency was compared.

An Engraved Bulbous-Necked Caddo Bottle from 41OR33 at the mouth of the Sabine River, Orange County, Texas

41OR33 is a large prehistoric shell midden deposit in Orange County, Texas, about 8.5 miles southwest of the city of Orange, at the mouth of the Sabine River and just north of Sabine Lake in Southeast Texas. Before the site was destroyed for road fill in October 1956, limited archaeological investigations had been done there by avocational archaeologists and then by E. Mott Davis of The University of Texas at Austin. During that work, a number of Native American burials were exposed and excavated, including one burial with an engraved bulbous-necked ancestral Caddo ceramic bottle. The bottle was donated by Edgar W. Brown, Jr. to UT in October 1956. I recently documented this vessel, which is a far-flung companion to bulbous-necked and spool-necked Caddo bottles from post-A.D. 1600 sites in the Red River and Ouachita River basins in East Texas and Southwest Arkansas as well as several post-A.D. 1600 sites in East Texas such as the Taylor site (41HS3) in the Big Cypress Creek basin.

ASSESSMENT OF THE EVOLUTION OF STORM SURGE IN COASTAL LOUISIANA

The Louisiana coastal landscape comprises an intricate system of fragmented wetlands, natural ridges, man-made navigation canals, flood protection and oil and gas infrastructure. Louisiana lost approximately 1,883 square miles (4,877 sq km) of coastal wetlands from 1932 to 2010 including 300 square miles (777 sq km) lost between 2004 and 2008 due to Hurricanes Katrina, Rita, Gustav and Ike (Couvillion et al., 2011). A projected additional 2,250 square miles (5,827 sq km) of coastal wetlands will be lost over the next 50 years if no preventative actions are taken (Coastal Protection and Restoration Authority of Louisiana, 2017). Storm surge models representing historical eras of the Louisiana coastal landscape can be developed to investigate the response of hurricane storm surge (e.g. peak water levels, inundation volume and time) to land loss and vegetative changes. Land:Water (L:W) isopleths (Gagliano et al., 1970; Twilley et al., 2016; Siverd et al., 2018) have been calculated along the Louisiana coast from Sabine Lake to the Pearl River. These isopleths were utilized to develop a simplified coastal landscape (bathymetry, topography, bottom roughness) representing circa2010. Similar methods are employed with the objective of developing storm surge models that represent the coastal landscape for past eras (circa1890, c.1930, c.1970).

Archaeological Investigations at the Mike Myers Site (41CE481) on Bowles Creek in Cherokee County, Texas

The Mike Myers site is a multiple component prehistoric site in the Bowles Creek valley in the Neches River basin in East Texas. The site is on an upland landform (400 ft. amsl), now a pasture with low surface visibility, between Bowles Creek to the east ca. 100 m and a spring-fed branch to the west. The confluence of Bowles Creek with Jackson Branch lies ca. 600 m to the south. Soils on the site are classified as Nacogdoches fine sandy loam. Based on the archaeological investigations conducted at the site to date, the known site area covers a ca. 150 x 60 m area (north-south and east-west) or approximately 2 acres, but the site may well extend to the south onto a lower upland ridge slope (390 ft. amsl) some distance; hopefully shovel tests can be excavated in this area in the near future to determine the full site boundaries. This article discusses the archaeological findings obtained to date from 2016 archaeological investigations at the Mike Myers site, much of it consisting of shovel tests across the site area, focusing particularly on the archaeological remains recovered in the work that date from Woodland and Caddo periods. Most notably, the shovel test work at the site recovered two sherds of non-tempered early Woodland period Tchefuncte pottery. As far as we are aware, this is only the second site in East Texas where Tchefuncte pottery has been found; the other site is the well-known Resch site (41HS16) in the Sabine River basin in Harrison County, Texas. Tchefuncte culture pottery has been recovered from the Louisiana Gulf Coast, in the Ouachita and Mississippi river basins in Mississippi, Louisiana, and southeast Arkansas, and in the Sabine Lake area of coastal Texas and Louisiana, more than 250 km east and southeast of the Mike Myers site.

Use of In Situ Burning as an Oil Spill Response Tool: Follow-Up of Four Case Studies

ABSTRACT Four in situ burning sites that varied widely in the physical setting, oil type, timing of the burn, and post-burn treatment were assessed 0.5–1.5 years post-burn: two condensate spills in intertidal marshes at Mosquito Bay, LA in April 2001 and near Sabine Lake, LA in February 2000; crude oil spill in a ponded wetland in Minnesota in July 2000; and a spill of diesel in a salt flat/wetland north of Great Salt Lake, UT in January 2000. When used quickly after a release, burning is most effective at reducing damage to vegetation and the areal extent of impact. Where crude oil was burned within hours after the release at the Minnesota site, the impact area was restricted to 3 acres. In contrast, the diesel in the Utah spill spread over 38 acres within 3 days. The window of opportunity for in situ burning to be an effective means of oil removal can be days to months, depending on the spill conditions. The condensate spill at Mosquito Bay site was effectively burned 6–7 days after the release was reported. For spills with snow and ice cover, burning may still be effective months later. In fact, it may be necessary to consider additional burns during thaw periods and during the final thaw. Burning will not reduce the toxic effects of the oil that occurred prior to the burn. It can, however, be very effective at reducing the extent and degree of impacts by quickly removing the remaining oil. In three of the four case studies, the area burned was significantly larger than the oiled area (up to 10 x). Healthy, green, unoiled vegetation is not always an effective fire break, particularly downwind; fires can quickly jump the kinds of fire breaks placed during spill emergencies in wetlands (e.g., vegetation laid down by the passage of airboats).